Tunnel-boring machines for Muni’s Central Subway project are set to arrive in San Francisco this week, with digging expected to begin in June.
The two massive machines — which each are more than 300-feet long — will take about four to six weeks to assemble once they arrive from China, according to Sarah Wilson, an engineer on the project. Once built, the machines will be dropped into a launch box below Fourth Street, where they will start drilling at about 40 feet per day, Wilson said.
Crews of six to nine people will man the massive machines, which will dig as deep as 150 feet below the surface. The machines are expected to reach their extraction site in North Beach next April, about 10 months after the start of work.
Along with heralding the arrival of its tunnel-boring machines, Muni recently announced the return of bids for a massive construction project. All three bids for the work, which includes the construction of three Central Subway stations, came back significantly higher than the agency’s original estimate.
Tutor Perini submitted the lowest offer at $840 million and will likely be awarded the work, according to Central Subway project manager John Funghi. Muni projected the work would only cost $720 million to $750 million, although Tutor Perini’s bid still falls within budget, Funghi said. That bid will need to be approved by the agency’s board of directors.
The $1.6 billion Central Subway project will extend Muni’s underground Metro service from South of Market to Chinatown.